I've been thinking on this myself. I have a relatively new bike bought earlier this year. But the model I wanted (Trek Checkpoint SL 5) only came in two colors, matte silver/grey and a radioactive red. I like deep reds, but this red was bright red, so I went with the silver/grey. But aside from being quite conservative, the matte finish bugs me. So, I've been thinking, what the heck, I could paint or have it painted.
However, I also have an itch to convert it to Shimano Di2 electronic shifting. So, between a pro paint job and Di2, I'm now thinking of just getting another bike. Maybe go full Trek Project One. If I repaint the existing bike, I would only have an MTB to ride while the work is done (weeks months?). Also, as it is now, any major damage to my Checkpoint and again, I would only have the MTB to ride. So, a second bike more suited for the road avoids being without a road type bike during painting as well as I have a backup if something happens to one bike.
So, my current view has more to do with the big picture rather than whether a given bike is worth repainting. I doubt repainting any bike, for other than a restoration, is worth it in terms of adding value to the bike.
If I had a bike that wasn't especially expensive (worth less than $1,000 used) and I also had another bike to ride while working on the first, I'd give the DIY approach with the high quality spray cans a go. No matter how bad it comes out, you can always strip it down and try, try again.